Patellofemoral pain (PFP) is a frequently encountered overuse disorder that involves the patellofemoral region and often presents as anterior knee pain. PFP is characterized by pain around or behind the patella that is aggravated by one or more activities that involve loading the patellofemoral joint during weight bearing on a flexed knee, and that cannot be attributed to another discrete intra-articular (eg, meniscus tear) or peripatellar (eg, patellar tendinopathy) pathology. PFP is the most common cause of knee pain seen by primary care physicians, orthopedic surgeons, and sports medicine specialists [1,2]. The etiology of PFP remains unclear, and diagnosis and treatment can be challenging. Research suggests that PFP is often recalcitrant and symptoms can persist for years [3].

Patellofemoral pain (PFP) can be defined as anterior knee pain involving the patella and retinaculum that excludes other intraarticular and peripatellar pathology. PFP describes a symptom complex and is a diagnosis of exclusion.

The terminology used to describe PFP is used inconsistently and can be confusing. Common synonymous terms include retropatellar pain syndrome, runner's knee, lateral facet compression syndrome, and idiopathic anterior knee pain. The term chondromalacia patella is used to describe pathologic changes in the articular cartilage of the patella, such as softening, erosion, and fragmentation. While frequently confused with PFP, chondromalacia patella is a pathologic diagnosis and constitutes a distinct cause of knee pain [4].

EPIDEMIOLOGY

Patellofemoral pain (PFP) is among the most common diagnoses in sports medicine. Although PFP is often seen in active individuals and may account for 25 to 40 percent of all knee problems seen in a sports injury clinic, the true incidence is not known [5]. PFP affects many running athletes and constitutes nearly 25 percent of all identified knee injuries [6-8]. (See "Overview of running injuries of the lower extremity".)

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